European regulators said that Biogen Idec Inc.'s drug Tecfidera is entitled to a decade of market exclusivity, protecting it from generic competition and ending months of uncertainty over the drug's future in the world's second-largest pharmaceutical market after the U.S.

A final approval decision for Tecfidera, a new multiple sclerosis treatment, is expected in the next two months and is widely expected to be positive. The company can then begin selling the drug in the European Union early next year, a key market...